Porous filtering-plate and process of making such filtering-plate.



UNITED STATES PATENT OFFICE- PETER D. GRAY, OF SAN FRANCISCO,CALIFORNIA, ASSIGNOR TO TONE RANDOLPH GRAY, OF SAN FRANCISCO,CALIFORNIA.

Specification of Letters Patent.

Patented Dec. 3, 1907.

Application filed June 3. 1907- Serial No. 377.119.

To all whom it may concern:

Be it known that I, PETER'D. GRAY, a citizen of the United States,residing at San Francisco, in the city and county of San Francisco andState of California, have invented new and useful Improvements in P0-rous Filtering-Plates and in Processes of Making such Filtering-Plates,of which the following is a specification.

This invention relates to porous plates used in filtering liquids andthe process of producing the same, and has for its object to secure afiltering material, non-injurious, and which on account of its chemicalinactivity will not rust or corrode, and which may be used for filteringpurposes indefinitely. I attain'this result, in the manner hereinafterdescribed, by adding to a quantity of pure block tin a solublesubstance, such as sodium chlorid, in a suificient quantity to securethe degree of porosity desired, and then dissolving out the solublesubstance. Considerable difficulty has been encountered heretofore inproducing a filtering material of the required degree of porositydesired, chemically inert to the action of water, and at the same timeofsuificient tensile strength to resist pressure. Through the methoddisclosed herein these results are obtained.

It may be remarked that instead of the sodium chlorid mentioned hereinthere may be used any of the soluble alkali salts or alkaline earthsalts, with the exception of the caustic alkalies, as the effect of thelatter would be to convert the tin into salts of stannic acid. It istherefore not my desire to confine myself solely to the use of sodiumchlorid.

Inasmuch as different degrees of porosity of the filtering material maybe desired under different conditions, it is impracticable to state as ageneral rule for all instances the exact proportion of sodium chlorid toblock tin. It will be sufficient to say that the filtering material maybe made more or less porous by the greater or less amount of sodiumchlorid used, the more sodium chlorid used tending to make the materialmore porous, and the less sodium chlorid used tending to make thematerial less porous. In the following description it may be assumedthat ten parts of pure block tin are used to one part of sodium chlorid.

A quantity of pure block tin is placed in a suitable receptacle andsubjected to a sufficient degree of heat to fuse it; it is then stirreduntil the wliole mass is in a liquid form. Sodium chlorid is then addedand the two ingredients thoroughly intermixed by again stirring untilhomogeneity is secured. The mixture while still inflits liquid form ispoured into a suitable mold and allowed to 0001 under high pressureuntil it has solified, the solidification usually taking place in fromthree to five minutes. The plate is further compressed by passing itthrough rollers. The plate is then placed in boiling water and allowedto remain until the sodium chlorid has been completely dissolved out.Practice has demonstrated that the dissolving out of the sodium chloridis materially hastened by an occasional change of water and by theaddition of a small quantity of alum. By the process described ahomogeneous porous filtering plate of pure block tin is obtained.

Having thus fully described my invention, what I claim as new, anddesire to secure by Letters Patent, is:

1. A porous filtering plate composed of pure block tin made porous bythe admixture of a soluble substance, substantially as described.

2. A porous filtering plate composed of pure block'tin made porousby theadmixture of a soluble substance and the dissolving out of the solublesubstance, substantially as described.

3. The process of making a porous filtering plate composed of pure blocktin made porous by an admixture of a soluble substance, by compressingand molding the said materials into shape and finally by dissolving outthe said soluble substance, substantially as described.

4. The process of'making a homogeneous porous filtering plate of pureblock tin, first by admixing therewith a soluble substance, second bymolding the two ingredients into shape, and third by dissolving out thesoluble substance,-substantially as described.

PETER D. GRAY.

It is hereby certified that in Letters Patent N 0. 872,621, grantedDecember 3, 1907, upon the application of Peter D, Gray, of SanFrancisco, California, for an improvement in Porous Filtering-Plates andProcesses of Making Such Filtering-Plates, an error appears in theprinted specification requiring correction, as follows: In line 64 theWord solified should read soiidzfied; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office.

Signed and sealed this 4th day of February, A. D., 1908.

[SEAL] o. o. BILLINGS,

Acting- Commissioner of Patents.

Correction in Letters Patent No. 872,621.

